This invention relates to a shaft seal assembly which includes a form-retaining shaped housing having an outer circumferential surface intended to be in frictional engagement with a first (stationary) machine component and a runner ring surrounded by the housing and intended for insertion on and frictional contact with a second (rotary) machine component. At least one sealing lip made of an elastic material is in a sliding engagement with an outer cylindrical face of the runner ring. The assembly further includes a sealing body situated between a radial annular leg part of the runner ring and the housing.
German Offenlegungsschrift (application published without examination) No. 3,120,795 discloses a shaft seal assembly situated between a stationary and a rotary machine component. The shaft seal assembly comprises two coaxially arranged form-retaining parts which are form-fittingly inserted into one another by means of collar-like, angled and axially extending attachments. The sealing lips of an elastomer body formed at the radial annular leg portion of the stationary seal assembly part engage the corresponding running face of the rotary seal assembly part. An annular sealing body made of a porous filter material, for example, an open-cell polyurethane which may be elastically compressed in the installed state, is situated axially between the two seal assembly parts. It is the purpose of the sealing body to prevent penetration of foreign bodies, such as fragments, dust or mud, into the sealed zone. The sealing body is elastically compressible and thus generates a certain biasing force. It is a disadvantage of this prior art construction that a significant friction is generated between the runner ring and the sealing body because of the relative rotation of large surface areas. This circumstance, dependent upon the selection of the material, causes a relatively rapid loss of the biasing force and may even lead to the destruction of the sealing body.